Illuminated markers of various sorts are fixed to the environment to inform approaching vessels of obstacles that might pose a risk of a collision with the vessel or for indicating the appropriate route. In sea navigation, such markers are called navigational aids, which may take the form of lighthouses, buoys, fog signals, day beacons etc. In aviation, tall buildings, bridges and the like are provided with flight obstacle illuminators for warning an approaching aircraft of the presence of an obstacle. EP 2541134 A2, for example, discloses a flight obstacle illuminator with a plurality of light emitting components arranged inside a respective plurality of lenses.
There is regulation concerning the specification of illuminated markers. The output of flight obstacle illuminators, for example, is regulated by standards drawn up by local and international aviation bodies such as the International Civil Aviation Organization (ICAO). Volume 1 (Aerodrome Design and Operations) of Annex 14 to the Convention on International Civil Aviation by the ICAO, for example, contains strict minimum requirements for the output light pattern of flight obstacle illuminators. The regulations vary around the World. Common to all such regulations is that the desired light pattern should be directed to all horizontal directions around the illuminator at quite a narrow beam spread in the respective vertical planes. In other words, the light pattern should peak at a zero line, which is the horizontal radial direction from a leveled flight obstacle illuminator.
There are, however, also recommendations for maximum output light pattern. Many of the modern standards pose desired maximum values for the intensity of light directed to different vertical deviations from the zero line. When examining the light intensity of the light pattern in the vertical plane, the desired light pattern should have a relatively narrow peak section surrounded by decreased intensity sections at both sides of the peak, which decreased intensity sections are further surrounded by trailing low intensity sections further apart from the zero line. The decreased intensity sections between the peak and trailing low intensity sections create so called shoulders to the light pattern. Indeed, the required minimum and recommended maximum values define quite a narrow tolerance for the desired shape of the output light pattern.
It is therefore an object to provide an illuminator suitable for use as a flight obstacle illuminator or navigational aid having a controlled output light pattern that will not only achieve an adequate minimum output light pattern but also not exceed recommended maximum values for a given vertical deviation from the zero line.